This invention relates to improvements in the rehabilitation of water supply pipes.
Domestic water supply systems are usually connected to the water company""s main by a service pipe, in two parts, the water company""s pipe making an end to end junction with the customer""s pipe at the highway boundary. A major public health problem remains the large number of premises which are still equipped with lead pipes, as the slightly soluble lead is a well known cumulative poison. One approach to this problem has been to replace lead piping with polyethylene plastics tubing. Alternative ductile metals such as copper have their own cumulative hazards.
As an alternative to replacement of lead pipes, it has been proposed to line the pipes with a polyethylene film which is everted by fluid pressure into the pipe (see WO97/04269) or a polyethyleneterephtalate (PET) film which is extruded as a profile and inflated by fluid pressure when heated in situ. This presses the lining against the inner walls of the pipe, and softens the lining to achieve a measure of thermal bonding to the pipe wall.
The known techniques all involve significant investment in capital plant and equipment, including those outlined above and also the use of impact moles (usable in compactable soils but not capable of being steered around obstructions such as other utility conduits gas, sewage, electricity, etc . . . ), pipe pulling, pipe splitting, guided drilling, pipe pushing, narrow trenching rods and powerful vacuum excavators.
An object of the present invention is to provide a simpler and cheaper trenchless method by which existing lead water pipes, particularly underground pipes, can be rehabilitated with the minimum of disruption to the customer""s property and without the need for expensive plant and equipment.
According to the invention, there is provided a method of rehabilitating water supply pipes comprising deploying a tubular liner within a pipe, characterized in that the liner comprises a polyolefin elastomer or a polyolefin plastomer. A polyolefin elastomer has a density below 870 kg/m3, whereas polyolefin plastomer has a density above 870 kg/m3.
The invention also provides water supply pipes which comprises a tubular liner of a polyolefin elastomer or plastomer and an apparatus for making water supply pipe and using the method of rehabilitating water supply pipes.
The polythene elastomer/plastomer preferably comprises a substantially linear ethylene interpolymer, which may comprise 50-95% by weight of ethylene, and 5-50% by weight of at least one olefinic co-monomer, preferably 10-25% by weight of the co-monomer. Co-monomers may contain from 3 to about 20 carbon atoms, and may comprise one or more of propylene, 1-butene, 1-hexene, 4-methyl-l-pentene, 1-heptene, and 1-octene. The density range may be in the range of 830 to 967 kg/M3, preferably 863 to 913 kg/m3 and more preferably 885 to 913 kg/m3, for optimum toughness and flexibility. Preferred co-monomers are 1-hexene, and especially 1-octene.
The substantially linear inter-polymers are advantageously characterized by a narrow molecular weight distribution, especially from 1.8 to 2.2 and a homogenous co-monomer distribution.
The tubular liner preferably is formed as a pleated tube formed with longitudinally extending multiple radial pleats, giving a star shaped multilobed or fluted cross-section. The tube is preferably formed with six radially equispaced pleats, defining an equal number of outwardly projecting lobes.
The liner may be deployed within a pipe, by securing one end of the liner adjacent an end of the pipe to which access has been obtained, and pulling the liner through the pipe by means of a line which may be attached to a foam messenger pig and propelled through the pipe by fluid pressure. Alternatively the liner may be pushed and pulled through the host pipe by means of a flexible rod attached to the liner.
The liner is preferably extruded in the pleated tube form from the polyolefin elastomer/plastomer, and has an outer diameter significantly smaller than the internal diameter of the pipe to be rehabilitated,
The liner may be die drawn during the extrusion process whilst the material is at just below the crystallisation melt temperature of the polymer, to impart a significant reduction in size of the extrusion as compared with the die, and also produces significant orientation of the polymer in the axial direction of the extrusion. This orientation in the direction of extrusion provides stiffness and resistance to kinking.